People may lose their balance for many reasons. Some may trip over an obstacle, lose their balance and fall. Others may lose their balance sensation, so that they can no longer stand or walk safely. Old people, in particular, may be slow in responding to changes in their balance; consequently they may have difficulties in regaining balance, when encountering sudden weight shifts (forward, backwards or sideways). By the time they react and try to move a foot, to regain balance, the fall process has already progressed beyond prevention. Some old people use a walking cane or a four-legged support device that provides them with a stabilizing moment to support any sway of their body weight. Such supporting devices are cumbersome, heavy to carry, and some are reluctant to use them because they view these devices as degrading.
Typically, a person is said to be in balance, when his center of mass is positioned over his support area.
The support area of each foot is the contact area of that foot with the surface below, and if a person is standing with one foot up (in a stationary position) his center of mass would have to be over the support area of the foot which is in contact with the ground. If a person is standing stationary, then his center of mass lies within the combined support area of his both feet, which is the area physically covered by the feet and the area between them.
When a person walks, his center of mass (together with his inertial momentum) shifts in position between both his feet. This is a dynamic state that evolves during the gait of the person (see FIG. 7d, that illustrates the shift in the center of mass in normal gait, and FIG. 7e, that illustrates the shift in the center of mass in typical elderly people).
The present invention addresses situations of loss of balance, both in static cases (when a person is stationary) and dynamic cases (when a person is walking).
The problem of falling is related to the mechanism in which a standing person maintains his balance. The sensory elements of the brain interpret, any shift of the body's center of weight, relative to both feet, by sensing the distribution of weight of the body over the support area of the feet. A shift of body weight forward or backward can be detected by sensing the weight distribution between the front and back areas of the foot. A shift of body weight sideways can be detected by sensing the weight distribution between the two legs.
In a standing position, when the body feels any imbalance toward the back it tries to counter it by moving more weight support to the heels. This creates a forward torque that returns the center of body weight forward, above the feet. When the body feels imbalance toward the front, it gives more support to the front of the foot, pushing the body center to the back. When the body experiences weight imbalance to one of the sides it shifts more support to that side. If a person is too slow to respond the center of weight may move over the heels, toes or over one of his legs, and balance may be regained only by displacing the foot and executing a step. For older people who may be weak and slow to response, the foot movement may come too late, thus a fall may be inevitable.
A main object of the present invention is to provide a device and method for assisting the user in regaining balance, by moving his foot in the desired direction, such that the center of body weight is returned over the support area
Automatic servo walking tools have been demonstrated before. They are based on the mechanism of walking by shifting the legs position in steps. They have never become practical in use because of the large electric motors necessary to assist the human body walking mechanism, and the lack of low weight power source in the form of electric batteries. Another aim of the present invention, is to facilitate a shift of the body weight with a burst of power that is needed only for intermittent periods, thus assisting the user in regaining his balance. Using only power bursts for regaining balance enables the device to be based on a simple low cost battery to power a motor.